barcelona :: formal | informal

When I first looked at a map of Ciutat Vella, Barcelona's old town, I filed it as informal, unplanned, medieval, etc. The more I learned about it, though, I came to realize it is a result of a process of many years of densification - in fact with a surprising level of underlying order. Here is a map of Barcino today with its original Roman grid overlaid. The red indicates straight avenues that were carved out of the urban fabric in the late 19th century. Notice how they are informed by the Cardo-Decumanus (darker black lines). 

This kind of organic change through the middle ages occurred all over the former Roman Empire, turning towns like Barcino into what we see below, and similarly Islamic cities like Aleppo and Damascus reclaimed their organic forms from the imposed Greek and Roman grids.

When urban blocks are too large for a human scale, transverse itineraries are created. This is the new road network seen below. But could we consider itineraries in a hierarchy - larger roads for autos, smaller roads for bikes and pedestrians?